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Thread: Fuel Pressure Gauge - 460 CID Ford Engine

  1. #1

    Fuel Pressure Gauge - 460 CID Ford Engine

    My fuel gauge going into my Mighty Demon carburetor is showing only a little above 4 PSI. The MD manual says the carburetor should receive 6 1/2 to 7 PSI.

    Randy at Cobra Valley says 5 1/2 to 6 psi is better. But he said that the gauges can build up pressure that can lead to incorrect readings.

    My gauge is an Allstate, liquid-filled. Randy recommended that I remove the gauge, pull off the rubber plug, drain the fluid, then drill a tiny hole in the rubber plug (a breather hole), and then reinstall the plug and the gauge. But they must have the liquid in there for a reason.

    Should I just let things alone, since I am not going to be racing? Is 4 PSI OK for moderate driving? But I don't want the A/F mixture to go lean if I push the RPMs a bit. BTW, my fuel pump is a Carter.

    The other problem is I've got a slight leak around the short section of rubber hose (about 2 inches) between the fuel filter and the fuel pump (I thinks). I tightened the clamps but the hose looks due for replacement. It seems to me there is no way to replace the hose section without gas pouring out of the fuel filter. Should I just run the tank low, have a couple 6 gallon gas cans ready, and replace the hose?

    I am getting more comfortable driving the car, and love it. It is an absolute gas to run it thru the gears, hearing that exhaust roar, being put back into my seat, and hitting 80 mph in about 5 seconds.

    Thanks fro any kind comments.

  2. #2
    Senior Member Funding Member DanEC's Avatar
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    Fuel pressure of 4 psi is on the low side but I guess it depends on how accurate the gauge reading is. Can you find another gauge to borrow and try it? I would tend to agree with Randy on the 5-1/2 to 6 psi.

    I would not worry about changing the rubber hose out at the fuel pump. If the car has been sitting a day or so and the tank is not plumb full, most fuel will have drained back towards the tank. Any that drains out should be pretty minimal.

    What might be more of a concern is if there is another rubber section connecting the tank to the fuel line. If so, logic says that if the front one is going bad the rear one probably is too. Those can be a problem. I changed the one out on my 66 Corvette last summer thinking that if I taped over the cap vent hole, enough vacuum would develop to slow down the leak enough to change over the hose. Somehow this didn't work but fortunately I pulled the end off of the fuel line so I could use a set of vice grips to shut off the hose from the tank. I ended up having to drain about 6 gallons of gas out into a drain pan and pour into my lawn mower fuel cans. It can depend on the design of the fuel tank and how it's plumbed and I'm not sure of how Superformance tanks are set up.
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    GROUCHY FUC***G OLD APE Funding Member Silverback's Avatar
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    First off I'm going to say that Randy is very knowledgeable, but like anybody we all have our weak links. Ron and/or Nomad can jump on that one for me.

    Okay, I'm going to start with a question. Do you have a mechanical fuel pump or just the electrical pump. Mechanical pumps have more pulsation due to their design and function than an electrical pump. The fluid in the fuel pressure gauge dampens that pulsation. So I will disagree with Randy on this and say don't drain the fluid from the gauge.

    Is the fuel pressure causing you any issues? If not, don't f*ck with it. And long before you damage any parts from a lean condition you will notice a stumble or something like that. You will only damage the engine if you continue to keep your foot in it. And if you are dumb enough to do that then you deserve what happens.

    Let us know about the fuel pump situation and we can go from there.

  4. #4
    Senior Member Funding Member Morris's Avatar
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    Quote Originally Posted by Bud74 View Post
    Randy at Cobra Valley says 5 1/2 to 6 psi is better. But he said that the gauges can build up pressure that can lead to incorrect readings.

    My gauge is an Allstate, liquid-filled. Randy recommended that I remove the gauge, pull off the rubber plug, drain the fluid, then drill a tiny hole in the rubber plug (a breather hole), and then reinstall the plug and the gauge. But they must have the liquid in there for a reason..
    Bud ...what Randy is talking about is as the engine heats up ....it will heat up the fluid in the fuel pressure gauge....which will give you a incorrect reading.....most use a dry gauge so they don’t get the fluctuation in the fuel pressure reading....& 6-7# lbs is fine....you won’t go lean unless you run out of fuel or change the jets.....have fun...

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    Administrator Funding Member Ron77's Avatar
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    Bud,

    I ran a dry gauge and right at 7 pounds of pressure all the time I had my Cobra. Maybe check all of your rubber fuel hoses and as for the one going to the carb, let the car set for a night and then I used to put a big rag under my hose when I had to replace it or take it off for any reason. That way the rag will soak up any gas that comes out and it won't be on the intake manifold.

    I am happy that you are driving the Cobra and really enjoying it.

    Ron


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  6. #6
    Quote Originally Posted by Silverback View Post
    First off I'm going to say that Randy is very knowledgeable, but like anybody we all have our weak links. Ron and/or Nomad can jump on that one for me.

    Okay, I'm going to start with a question. Do you have a mechanical fuel pump or just the electrical pump. Mechanical pumps have more pulsation due to their design and function than an electrical pump. The fluid in the fuel pressure gauge dampens that pulsation. So I will disagree with Randy on this and say don't drain the fluid from the gauge.

    Is the fuel pressure causing you any issues? If not, don't f*ck with it. And long before you damage any parts from a lean condition you will notice a stumble or something like that. You will only damage the engine if you continue to keep your foot in it. And if you are dumb enough to do that then you deserve what happens.

    Let us know about the fuel pump situation and we can go from there.
    Right - if it ain't broke, don't fix it. It is not causing me any problems. My fuel pump is electric - a Carter. Thanks all for the good advice.
    Last edited by Bud74; 04-06-2021 at 05:55 AM.

  7. #7



    FYI These show the wet fuel filter and wet hose section between my fuel filter and electric pump.

  8. #8
    If that's the Carter P60430 it is 6psi max. Wet fuel pressure gauges are inaccurate due to heat so should not be used as an absolute reading but OK for a sanity check (have pressure).

  9. #9
    Senior Member Funding Member DanEC's Avatar
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    I assumed you had a mechanical fuel pump. Yes, replacing the hoses on that undercarriage assembly can be a mess. I would try running the tank as low as you can. Then get a clean catch can and a few gas cans. Clamp the rubber fuel line with needle nose vise grips or similar, remove the fuel hose connection closest to the engine and let the residual fuel downstream drain out, then relax the vice grips and let it fill the catch pan, clamp the line, pour the pan into your gas cans, repeat until flow stops. I would replace all the rubber sections then.
    Our world is not divided by Race, Color, Gender or Religion. Our world is divided into wise people and fools. And fools divide themselves by Race, Color, Gender or Religion.

    Nelson Mandela

    "Don't underestimate Joe's ability to f--- things up."

    Barack Obama

  10. #10
    Quote Originally Posted by DanEC View Post
    I assumed you had a mechanical fuel pump. Yes, replacing the hoses on that undercarriage assembly can be a mess. I would try running the tank as low as you can. Then get a clean catch can and a few gas cans. Clamp the rubber fuel line with needle nose vise grips or similar, remove the fuel hose connection closest to the engine and let the residual fuel downstream drain out, then relax the vice grips and let it fill the catch pan, clamp the line, pour the pan into your gas cans, repeat until flow stops. I would replace all the rubber sections then.
    Thanks DanEC.

  11. #11
    Quote Originally Posted by Nrotoxin View Post
    If that's the Carter P60430 it is 6psi max. Wet fuel pressure gauges are inaccurate due to heat so should not be used as an absolute reading but OK for a sanity check (have pressure).
    MY Carter is stamped 3D17A 43.

  12. #12
    The Carter fuel pump part numbers start with a "P".

  13. #13
    Quote Originally Posted by Nrotoxin View Post
    The Carter fuel pump part numbers start with a "P".
    Thanks - I guess I will have to jack the car up again and look harder to find that part number.

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